The Mill Creek Net Zero Home has a cold room built under the front porch.

The cold room, or root cellar, has long been a friend to those living in northern climates. It takes advantage of the fact that the temperature six feet underground remains a relatively constant temperature year-round. Therefore, it keeps the room cool in summer, and warm enough not to freeze in winter.

Our cold room has been working perfectly since it was built. During the winter it is about as cold as a fridge. Our potatoes and garlic are still in perfect condition four months after harvest! Plus I only need to buy beer a couple of times a year.

The room is about 6’ x 10’. It is thermally separated from the rest of the house, and we don’t actively heat or cool it. Its concrete floor was poured directly onto the earth because we actually want the heat/cold from the earth to enter the room.

Cold room, Mill Creek Net Zero Home

We insulated the interior of the walls with two inches of polyisocyanurate board (about R7 per inch), and added R28 worth of pink insulation in the ceiling. There are also two vents to the space (see above picture), but we’ve kept them plugged with rags so far. The idea is that we could attach a fan to one of them that runs during the Fall and Spring nights to further cool the space. The concrete floor acts as a heater (in winter) or a heat sink (in summer).

Some construction details: when you are standing on the front porch, there is 5” concrete on a reinforced 8” grid, a layer of plywood, 7.25” of pink insulation, and then another finishing layer of plywood under you.

The room is thermally separated from the heated space.

A reused interior door was insulated by gluing a spare piece of foam to it.

Our cold room provides us with a free way to store food from the garden long-term. It would easily act as a fridge for milk and such during the winter if we ever needed it to.

It saves us energy in today's world, and it provides us a hedge against future disruptions to our energy supply. I suspect that we will be very grateful for this cold room at some point along the way.

During the past 31 days the house consumed 1810 kWh and produced only 152 kWh. OUCH!

Our total consumption to date (since October 18) is 3986 kWh, with total production at 724 kWh. Since our total annual consumption budget is 8000 kWh, we’ve burned through 50% of our electricity budget.

Sounds pretty bad right? The game isn’t over just yet. We’ve just come through three of the four darkest months of the year. By February 15, we will be getting as many sunshine hours as we do on October 27. Plus, last year we virtually stopped heating the house as of the second week of February (due to a sunny, mild month).

So we are still in the ballpark, but we will definitely need some luck for this to be a net zero energy year.

Mill Creek NetZero Home's electricity, as measured by the TED 5000 and published by Google Powermeter

The Solar Energy Society of Alberta (SESA) has been a stalwart member of Edmonton’s green community for many years. They have a great web resource here, and their seminar series has been a vital resource for showcasing the cutting edge of solar and efficiency technologies deployed in Alberta over the past decade.

I’m grateful that SESA saw fit to purchase a TED 5000 electricity monitor for installation in the Mill Creek Net Zero Home. The TED 5000 allows us to measure four flows of electricity (the main panel, the hot water tank, and both solar inverters). I hope that it will provide important data to Edmonton’s green community, and it will certainly be perfect for measuring our energy use during our net zero energy year. The data is published to the web automatically via Google Powermeter. I plan to write an app that will publish the data publically, but that is a ways off yet.